(1) Field of the Invention
The present invention relates to a novel lubricant for use with hydrogen-containing chloro-fluoro carbon and fluoro carbon refrigerants.
Particularly, the present invention relates to a novel lubricant for use in refrigerators and the like, which has a polyglycol chain and a phosphonitrile skeleton, and which has an excellent lubricity as well as good compatibility with hydrogen-containing chloro-fluoro carbon and fluoro carbon refrigerants.
(2) Description of the Prior Art
Generally, the refrigerator is a device in which the compressor serves to create a low temperature by means of repetitive liquefaction and vaporization of refrigerants, and this device consists of a vaporizer, a compressor, an expansion valve and the like, through which the refrigerants and the lubricant circulate to establish a cycle of absorption and release of the heat. Refrigerating oil which is dissolved in the refrigerant circulates the refrigeration systems and this lubricant serves to help operate the refrigeration equipments.
Refrigerating oil generally consists of naphthene or paraffin based mineral oils and alkylbenzene, with the addition of an antioxidant, 1 metal deactivator, an anti wear agent, a corrosion inhibitor, etc.
Therefore, the lubricant is required to have good compatibility with the refrigerant, stability in the presence of the refrigerant, lubricity for the instrument (anti wear, anti seize properties).
Refrigerators employ as refrigerants fluorine, chlorine and carbon, for example, trichloromonofluoromethane (R11), dichlorodifluoromethane (R12), monochlorodifluoromethane (R22) and the like.
Recently, a decrease in the use of chloro fluoro carbons was agreed to under the Montreal Protocol, for the purpose of protecting the ozone layer in stratosphere. Accordingly, the USA Environmental Protection Agency (EPA) recommended 6 hydrogen-containing chloro-fluoro carbon alternatives, namely, 1, 1-dichloro-2, 2, 2-trifluoroethane (HCFC-123), 1-chloro-1, 2, 2, 2-tetrafluoroethane (HCFC-124), 1, 2-dichloro-2, 2-difluoroethane (HCFC-132b), 1-chloro-2, 2, 2-trifluoroethane (HCFC-133a), 1, 1, 1, 2-tetrafluoroethane (HCFC-134a) and 1, 1-dichloro-1-fluoroethane (HCFC-141b). Among these, the use of 1, 1, 1, 2-tetrafluoroethane as an alternative for R-12 is brought into discussion because of its physical properties similar to those of R-12.
A polyalkyleneglycol base lubricant capable of applying to 1, 1, 1, 2-tetrafluoroethane was disclosed by Du Pont (U.S.A.) in Research Disclosure No. 17483 (October, 1978). Polyalkyleneglycol base lubricant was also disclosed in U.S. Pat. No. 4,755,316 (July, 1988).
Also in Japan, polyalkyleneglycol base lubricants have been studied and various polyalkyleneglycol derivatives have been developed, as disclosed in Published Japanese Patent Unexamined Application 1-198, 694, 1-259, 093, 1-259, 094, 1-259, 095, 2-43, 290, 2-84, 491, 2-102, 296, 2-140, 295, 2-242, 888, 2-258, 895 and 2-269, 195.